MMIC package

Abstract

Disclosed herein is an MMIC package which comprises a base substrate, a composite capacitor substrate made of a ceramics plate mounted on the base substrate, an MMIC bare chip which functions as a high frequency semiconductor element and face-down bonded on the composite capacitor substrate, and an electroconductive covering which covers, together with the base substrate, the MMIC bare chip. In order to suppress the deterioration of the electrical characteristics of the above MMIC, the above components are so arranged that the interconnection length between the components is made to be minimum.

Description

(a) Field of the InventionThe present invention relates to an MMIC (Monolithic Microwave IC) incorporating an MMIC bare chip which is a high frequency semiconductor element.(b) Description of the Related ArtFIG. 1 is a sectional view showing the structure of an example of conventional MMIC packages, and FIG. 2 is a perspective view showing the peripheral structure of MMIC excluding a cap. The conventional MMIC shown in these figures has a metal header 101 made of copper or copper-tungsten, an MMIC 102 die-bonded on the header, and a small plate 103 die-bonded onto the header 101 in the vicinity of a source terminal of the MMIC. The small plate 103 is prepared by plating the both surfaces of a ceramics plate acting as a substrate having a high dielectric constant, and functions as a capacitor formed between the opposing plated surfaces. The power supply from a power source to the MMIC 102, and the input and the output of high frequency signals are performed through external terminals...

AI Technical Summary

Benefits of technology

In accordance with the MMIC package of the present invention, the connection length between an electrode on the front surface of the MMIC bare chip and an external terminal of the package can be reduced so that the deterioration of the electrical characteristics due to the influence of unwanted inductance can be made minimum.

Problems solved by technology

In this case, its characteristics may be deteriorated during the mounting of the MMIC on the package even if the frequency range of the MMIC is designed to be broad because the frequency range capable of conducting the impedance matching is narrowed.

However, several problems arise for putting the above minimum connection length technique employing the bump to the practical use.

A first problem is that a bypass capacitor which depresses the impedance of the source line to a low level cannot be located just beneath the source terminal of the MMIC.

Since the interconnect length between the bare chip electrode and the wiring pad on the substrate is short in the flip chip mounting method, the stresses due to the difference between thermal expansion coefficients of materials and to shocks cannot be absorbed, which causes the MMIC to be brittle.

When the flip chip mounting method is applied as it is to an ordinarily designed bare chip, the resin sealing may not be performed depending on circumstances.

As a result, the connection with the GND surface formed on the substrate mounting the bare chip becomes difficult.

If the potential of the GND surface of the bare chip cannot be maintained the same as that of the GND surface of the mounting substrate, the electrical characteristics may be subject to adverse effects such as unnecessary resonance.

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